Casimr Funk discovered the first b vitamin 1912. He realised disease was caused by these vitamin deficiencies, and that other theories like germ theory are wrong. Here is one of his papers, and his book http://www.mv.helsinki.fi/home/hemila/history/Funk_1912.pdf https://archive.org/details/cu31924073915161 Choline is important, and deficiency is common.Google choline deficiency NCBI to find what it does in rats. Some studies on it's roles: http://sci-hub.tw/https://doi.org/10.1080/07315724.1992.10718251 http://zycia.com.au/publications/choline-needed-for-normal-development.pdf http://zycia.com.au/publications/nutritional-importance-of-choline.pdf There are plent of textbooks on nutritional biochemistry, and the b vitamins/minerals on libgen. Chronometer is a good website to track micro nutrient intake. Nutritiondata can be used to view the b vitamin content of food. A lot of b vitamins besides 9, and 12 can actually be blood tested check with doctor or pathology websites in ones country. Yeast, rice bran cereal, mixed nuts, wheat germ, wheat bran are some of the highest food sources of them.